Enforce same input tensor storage in VariableType functions (#16305)
Summary:
In VariableType.cpp, when a function modifies its input tensors, it should only change the input tensors' storage data in-place, and should never change the input tensors' storage pointers. This PR adds checks for this, and also fixes functions that fail this test.
This is part of the Variable/Tensor merge work (https://github.com/pytorch/pytorch/issues/13638).
Pull Request resolved: https://github.com/pytorch/pytorch/pull/16305
Differential Revision: D13897855
Pulled By: yf225
fbshipit-source-id: 0c4fc7eb530d30db88037b1f0981f6f8454d3b79
